Calcium is essential for building and maintaining strong bones and for the heart, muscles and nerves to function properly, according to the Mayo Clinic. Children who do not get enough calcium may have stunted growth. Adults need calcium to avoid osteoporosis. The daily requirement for dietary calcium varies from 1,000 milligrams for young men to 1,200 milligrams for women over the age of 51 and men over 71.
The body does not produce its own calcium, so it must be ingested in foods and supplements, says the Mayo Clinic. Some foods that contain calcium are dairy products, leafy green vegetables, fish with edible bones such as canned salmon or sardines, and fortified juice and cereals.
The body needs vitamin D to absorb calcium properly, according to the Mayo Clinic, so it can be difficult for those following a vegan diet to get enough calcium from foods. Calcium deficiency is also more likely in those with lactose intolerance or people who consume large amounts of protein or sodium, which cause the body to excrete calcium.
The Mayo Clinic lists other factors that can lead to calcium deficiency, such as osteoporosis, treatment with corticosteroids, and conditions such as celiac disease or irritable bowel syndrome. Calcium supplements are available in a variety of compounds, some of which also contain vitamin D. It is important to check the amount of elemental calcium in a supplement to ensure that the dosage is adequate.